N‐Heterocyclic Iod(az)olium Salts – Potent Halogen‐Bond Donors in Organocatalysis

This article describes the application of N‐heterocyclic iod(az)olium salts (NHISs) as highly reactive organocatalysts. A variety of mono‐ and dicationic NHISs are described and utilized as potent XB‐donors in halogen‐bond catalysis. They were benchmarked in seven diverse test reactions in which the activation of carbon‐ and metal‐chloride bonds as well as carbonyl and nitro groups was achieved. N‐methylated dicationic NHISs rendered the highest reactivity in all investigated catalytic applications with reactivities even higher than all previously described monodentate XB‐donors based on iodine(I) and (III) and the strong Lewis acid BF(3).